Signal modulator

ABSTRACT

A reflective modulator comprises a coupler, two diodes and two DC block units. The coupler has an input end used to output an output signal, an output end used to output an output signal, a first load end connected to one of the diodes and a second load end connected to another one of the diodes. The DC block units connect between the diodes and the coupler for DC blocking. A message signal is selectively inputted to both of the two DC block units for operating the state of the two diodes. A BPSK modulator using the reflective modulator and a quadrature modulator using the BPSK modulator are also introduced.

FIELD OF THE INVENTION

The present disclosure relates to signal modulators of a digitalmodulation system and, more particularly, to signal modulators of adigital modulation system, each of which can output an output signalaccording to one or more message signal.

BACKGROUND OF THE INVENTION

Signal modulator is an important part of the digital modulation system.Key features of signal modulators are RF bandwidth, modulationbandwidth, local oscillation drive power and modulation accuracy.Several types of signal modulators are Gilbert mixers, diode mixers,reflective modulators and so on. The Gilbert mixers have the advantagesof low loss, high harmonic suppression and high isolation, but have thedisadvantage of lower operating frequency, usually only below 10-GHz,and ease of DC power consumption. The diode mixers have the disadvantageof requiring a higher drive power of the local oscillator signal. Thereflective modulators have less influence on the phase and amplitudeerror caused by the process variation, and can have a wider operatingbandwidth and lower required local oscillator drive power. However,reflective modulators have the disadvantage of low isolation. Moreover,the reflective modulators use more passive circuits, and thus requiredcircuit area of the reflective modulators is quite affected by theoperating frequency.

Accordingly, it is imperative to provide signal modulators which canovercome the aforesaid drawbacks of the conventional signalmodulator(s).

SUMMARY OF THE INVENTION

In view of the aforesaid drawbacks of the prior art, it is an objectiveof the present disclosure to provide signal modulators featurebroadband, low insertion loss, low required local oscillation drivepower, low phase and amplitude imbalance, excellent modulation qualityand small required die area.

In order to achieve the above and other objectives, the presentdisclosure provides a reflective modulator which comprises a coupler, afirst diode, a second diode, a first DC (Direct Current) block unit anda second DC block unit.

The coupler has an input end, an output end, a first load end and asecond load end, the input end being used to receive an input signal,the output end being used to output an output signal. The input end isused to receive an input signal. The output end is used to output anoutput signal. The first DC block unit connects between the first diodeand the first load end of the coupler for DC blocking. The second DCblock unit connects between the second diode and the second load end ofthe coupler for DC blocking. A message signal is inputted to both of thefirst and second DC block units for operating the states of the firstand second diodes.

Regarding the reflective modulator, the first and second diodes turn onwhen the message signal is large enough, and the first and second diodesturn off when the message signal is not large enough.

Regarding the reflective modulator, the first DC block unit includes afirst capacitor and a first resistor, the second DC block unit includesa second capacitor and a second resistor, the first capacitor isconnected between the first diode and the first load end of the couplerfor DC blocking, the first resistor is connected with the firstcapacitor and the first diode, the second capacitor is connected betweenthe second diode and the second load end of the coupler for DC blocking,and the second resistor is connected with the second capacitor and thesecond diode.

Regarding the reflective modulator, the first and second diodes areimplemented by PIN diodes.

Regarding the reflective modulator, the input signal is generated from alocal oscillator and the output signal is used for radio frequency.

In order to achieve the above and other objectives, the presentdisclosure provides a BPSK modulator which comprises a balun, a firstreflective modulator, a second reflective modulator and a powercombiner.

The balun has a first conductor, a second conductor, a third conductorand a fourth conductor. The first conductor and the second conductor areconnected and used to have equal currents in opposite directions. Oneend of the third conductor magnetically couples to the first conductor.Another end of the third conductor connects to ground. One end of thefourth conductor magnetically couples to the second conductor. Anotherend of the fourth conductor connects to ground. A first input end of thefirst reflective modulator connects to the third conductor. A secondinput end of the second reflective modulator connects to the fourthconductor. The power combiner connects to a first output end of thefirst reflective modulator and a second output end of the secondreflective modulator. A first message signal is inputted to the firstreflective modulator. A second message signal is inputted to the secondreflective modulator. The first message signal and the second messagesignal are a pair of differential signals.

Regarding the BPSK modulator, the first reflective modulator comprises afirst coupler, a first diode, a second diode, a first DC(Direct-Current) block unit and a second DC block unit, the firstcoupler having the first input end, the first output end, a first loadend and a second load end, the first DC block unit connecting betweenthe first diode and the first load end of the first coupler for DCblocking, the second DC block unit connected between the second diodeand the second load end of the first coupler for DC blocking, the firstmessage signal inputting to both of the first and second DC block unitsfor operating the state of the first and second diodes.

Regarding the BPSK modulator, the second reflective modulator comprisesa second coupler, a third diode, a fourth diode, a third DC block unitand a fourth DC block unit, the second coupler having the second inputend, the second output end, a third load end and a fourth load end, thethird DC block unit connecting between the third diode and the thirdload end of the second coupler for DC blocking, the fourth DC block unitconnecting between the fourth diode and the fourth load end of thesecond coupler for DC blocking, the second message signal inputting toboth of the third and fourth DC block units for operating the state ofthe third and fourth diodes.

Regarding the BPSK modulator, the first and second diodes turn on whenthe first message signal is large enough, and the first and seconddiodes turn off when the first message signal is not large enough; andthe third and fourth diodes turn on when the second message signal islarge enough, and the third and fourth diodes turn off when the secondmessage signal is not large enough.

Regarding the BPSK modulator, wherein the first DC block unit includes afirst capacitor and a first resistor, the second DC block unit includesa second capacitor and a second resistor, the first capacitor isconnected between the first diode and the first load end of the firstcoupler for DC blocking, the first resistor is connected with the firstcapacitor and the first diode, the second capacitor is connected betweenthe second diode and the second load end of the first coupler for DCblocking, and the second resistor is connected with the second capacitorand the second diode

Regarding the BPSK modulator, wherein the third DC block unit includes athird capacitor and a third resistor, the fourth DC block unit includesa fourth capacitor and a fourth resistor, the third capacitor isconnected between the third diode and the third load end of the secondcoupler for DC blocking, the third resistor is connected with the thirdcapacitor and the third diode, the fourth capacitor is connected betweenthe fourth diode and the fourth load end of the second coupler for DCblocking, and the fourth resistor is connected with the fourth capacitorand the fourth diode.

Regarding the BPSK modulator, the first, second, third and fourth diodesare implemented by PIN diodes.

Regarding the BPSK modulator, an input signal is generated from a localoscillator and inputted to the balun, and an output signal is outputtedfrom the power combiner and used for radio frequency.

Regarding the BPSK modulator, the BPSK modulator is integrated in amonolithic microwave integrated circuit.

In order to achieve the above and other objectives, the presentdisclosure provides a quadrature modulator. The quadrature modulatorcomprises a Wilkinson power divider, a first BPSK (Binary Phase ShiftKeying) modulator, a second BPSK modulator and a Lange coupler.

The Wilkinson power divider has a power input end, a first power outputend and a second power output end. The first BPSK modulator connected tothe first power output end of the Wilkinson power divider. The secondBPSK modulator connected to the second power output end of the Wilkinsonpower divider, the second BPSK modulator generating a second outputsignal. The Lange coupler connected to the first BPSK modulator and thesecond BPSK modulator for receiving a first output signal and a secondoutput signal. A first message signal and a second message signal areinputted to the first BPSK modulator. A third message signal and afourth message signal are inputted to the second BPSK modulator. Thefirst BPSK modulator generates the first output signal according to thefirst message signal, the second message signal, and an input from theWilkinson power divider. The second BPSK modulator generates the secondoutput signal according to the third message signal, the fourth messagesignal, and an input from the Wilkinson power divider.

Regarding the quadrature modulator, the first BPSK modulator comprises afirst balun, a first reflective modulator, a second reflective modulatorand a first power combiner, the first balun having a first conductor, asecond conductor, a third conductor and a fourth conductor, the firstconductor and the second conductor being connected and used to haveequal currents in opposite directions, one end of the third conductormagnetically coupling to the first conductor and another end of thethird conductor connecting to ground, one end of the fourth conductormagnetically coupling to the second conductor and another end of thefourth conductor connecting to ground, a first input end of the firstreflective modulator connecting to the third conductor, a second inputend of the second reflective modulator connecting to the fourthconductor, the first power combiner connecting to a first output end ofthe first reflective modulator and a second output end of the secondreflective modulator, the first message signal inputting to the firstreflective modulator, the second message signal inputting to the secondreflective modulator, the first message signal and the second messagesignal being a pair of differential signals.

Regarding the quadrature modulator, the second BPSK modulator comprisesa second balun, a third reflective modulator, a fourth reflectivemodulator and a second power combiner, the second balun having a fifthconductor, a sixth conductor, a seventh conductor and an eighthconductor, the fifth conductor and the sixth conductor being connectedand used to have equal currents in opposite directions, one end of theseventh conductor connecting to the fifth conductor and another end ofthe seventh conductor connecting to ground, one end of the eighthconductor connecting to the sixth conductor and another end of theeighth conductor connecting to ground, a third input end of the thirdreflective modulator connecting to the seventh conductor, a fourth inputend of the fourth reflective modulator connecting to the eighthconductor, the second power combiner connecting to a third output end ofthe third reflective modulator and a fourth output end of the fourthreflective modulator, the third message signal inputting to the thirdreflective modulator, the fourth message signal inputting to the fourthreflective modulator, the third message signal and the fourth messagesignal being a pair of differential signals.

Regarding the quadrature modulator, the first reflective modulatorcomprises a first coupler, a first diode, a second diode, a first DC(Direct-Current) block unit and a second DC block unit, the firstcoupler having the first input end, the first output end, a first loadend and a second load end, the first diode connecting to the first loadend of the first coupler, the second diode connecting to the second loadend of the first coupler, the first DC block unit connecting between thefirst diode and the first load end of the first coupler for DC blocking,the second DC block unit connected between the second diode and thesecond load end of the first coupler for DC blocking, the first messagesignal inputting to both of the first and second DC block units foroperating the state of the first and second diodes.

Regarding the quadrature modulator, the second reflective modulatorcomprises a second coupler, a third diode, a fourth diode, a third DCblock unit and a fourth DC block unit, the second coupler having thesecond input end, the second output end, a third load end and a fourthload end, the third diode connecting to the third load end of the secondcoupler, the fourth diode connecting to the fourth load end of thesecond coupler, the third DC block unit connecting between the thirddiode and the third load end of the second coupler for DC blocking, thefourth DC block unit connecting between the fourth diode and the fourthload end of the second coupler for DC blocking, the second messagesignal inputting to both of the third and fourth DC block units foroperating the state of the third and fourth diodes.

Regarding the quadrature modulator, the third reflective modulatorcomprises a third coupler, a fifth diode, a sixth diode, a fifth DCblock unit and a sixth DC block unit, the third coupler having the thirdinput end, the third output end, a fifth load end and a sixth load end,the fifth diode connecting to the fifth load end of the third coupler,the sixth diode connecting to the sixth load end of the third coupler,the fifth DC block unit connecting between the fifth diode and the fifthload end of the third coupler for DC blocking, the sixth DC block unitconnecting between the sixth diode and the sixth load end of the thirdcoupler for DC blocking, the third message signal inputting to both ofthe fifth and sixth DC block units for operating the state of the fifthand sixth diodes.

Regarding the quadrature modulator, the fourth reflective modulatorcomprises a fourth coupler, a seventh diode, an eighth diode, a seventhDC block unit and an eighth DC block unit, the fourth coupler having thefourth input end, the fourth output end, a seventh load end and a eighthload end, the seventh diode connecting to the seventh load end of thefourth coupler, the eighth diode connecting to the eighth load end ofthe fourth coupler, the seventh DC block unit connecting between theseventh diode and the seventh load end of the fourth coupler for DCblocking, the eighth DC block unit connecting between the eighth diodeand the eighth load end of the fourth coupler for DC blocking, thefourth message signal inputting to both of the seventh and eighth DCblock units for operating the state of the seventh and eighth diodes.

Regarding the quadrature modulator, the first DC block unit includes afirst capacitor and a first resistor, the second DC block unit includesa second capacitor and a second resistor, the first capacitor isconnected between the first diode and the first load end of the firstcoupler for DC blocking, the first resistor is connected with the firstcapacitor and the first diode, the second capacitor is connected betweenthe second diode and the second load end of the first coupler for DCblocking, and the second resistor is connected with the second capacitorand the second diode.

Regarding the quadrature modulator, the third DC block unit includes athird capacitor and a third resistor, the fourth DC block unit includesa fourth capacitor and a fourth resistor, the third capacitor isconnected between the third diode and the third load end of the secondcoupler for DC blocking, the third resistor is connected with the thirdcapacitor and the third diode, the fourth capacitor is connected betweenthe fourth diode and the fourth load end of the second coupler for DCblocking, and the fourth resistor is connected with the fourth capacitorand the fourth diode.

Regarding the quadrature modulator, the fifth DC block unit includes afifth capacitor and a fifth resistor, the sixth DC block unit includes asixth capacitor and a sixth resistor, the fifth capacitor is connectedbetween the fifth diode and the fifth load end of the third coupler forDC blocking, the fifth resistor is connected with the fifth capacitorand the fifth diode, the sixth capacitor is connected between the sixthdiode and the sixth load end of the third coupler for DC blocking, andthe sixth resistor is connected with the sixth capacitor and the sixthdiode.

Regarding the quadrature modulator, the seventh DC block unit includes aseventh capacitor and a seventh resistor, the eighth DC block unitincludes a eighth capacitor and a eighth resistor, the seventh capacitoris connected between the seventh diode and the seventh load end of thefourth coupler for DC blocking, the seventh resistor is connected withthe seventh capacitor and the seventh diode, the eighth capacitor isconnected between the eighth diode and the eighth load end of the fourthcoupler for DC blocking, and the eighth resistor is connected with theeighth capacitor and the eighth diode.

Regarding the quadrature modulator, the first, second, third, fourth,fifth, sixth, seventh and eighth diodes are implemented by PIN diodes.

Regarding the quadrature modulator, an input signal inputted to thepower input end of Wilkinson power divider is generated from a localoscillator, and an output signal is outputted from the Lange coupler andused for radio frequency.

Regarding the quadrature modulator, the quadrature modulator isintegrated in a monolithic microwave integrated circuit.

In conclusion, the aforesaid signal modulators feature broadband, lowinsertion loss, low required local oscillation drive power, low phaseand amplitude imbalance, excellent modulation quality and small requireddie area.

BRIEF DESCRIPTION OF THE DRAWINGS

Objectives, features, and advantages of the present disclosure arehereunder illustrated with specific embodiments in conjunction with theaccompanying drawings.

FIG. 1 shows an equivalent circuit diagram of a diode being conductingand non-conducting;

FIG. 2 is a circuit diagram of a reflective modulator according to anembodiment of the present disclosure;

FIG. 3 is a detailed circuit diagram of a reflective modulator accordingto an embodiment of the present disclosure;

FIG. 4 is a circuit diagram of a BPSK modulator according to anembodiment of the present disclosure;

FIG. 5 is a circuit diagram of a BPSK modulator according to anembodiment of the present disclosure; and

FIG. 6 is a circuit diagram of a quadrature modulator according to anembodiment of the present disclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, FIG. 1 shows an equivalent circuit diagram of adiode being conducting and non-conducting. A diode can be equivalent toa small resistor (R_(on)) in a view of signal operations when the diodehas sufficient cross-voltage across the diode to conduct the diode andflow through a current. A diode can be equivalent to a small capacitor(C_(off)) in a view of signal operations when the diode does not havesufficient cross-voltage across the diode to conduct the diode and flowthrough a current. The diode conduction and non-conduction switchingcharacteristics can be used in reflective modulators.

Referring to FIG. 2, FIG. 2 is a circuit diagram of a reflectivemodulator according to an embodiment of the present disclosure. Thereflective modulator 100 comprises a coupler 110, a diode D1, a diodeD2, a DC (Direct Current) block unit 120 and a DC block unit 130. Thecoupler 110 has an input end 111, an output end 112, a first load end113 and a second load end 114. The input end 111 is used to receive alocal oscillating signal LO generated from a local oscillator. Theoutput end 112 is used to output an output signal RF which the localoscillating signal LO is modulated by a message signal BB.

The first DC block unit 120 is connected between the first diode D1 andthe first load end 113 of the coupler 110 for DC blocking. The second DCblock unit 130 is connected between the second diode D2 and the secondload end 114 of the coupler 110 for DC blocking.

A message signal BB is selectively inputted to both of the DC blocksunit 120 and the DC block unit 130. The diodes D1 and D2 turn on whenthe message signal BB is inputted to the DC block units 120, 130 andgoes through the bias paths P1, P2, i.e. the message signal BB is largeenough to turn on the diodes D1 and D2. The diodes D1 and D2 turn offwhen the message signal BB is not large enough.

The reflection coefficient of the coupler 110 changes according to thestate of the diodes D1, D2. That is, the refection coefficient of thecoupler 110 corresponding to the conducting states of the diodes D1, D2is not the same as that corresponding to the non-conducting states ofthe diodes D1, D2. The phase of the output signal RF is also changed bythe states of the diodes D1, D2, and that is the phase of the outputsignal RF corresponding to the conducting states of the diodes D1, D2 isnot the same as that corresponding to the non-conducting states of thediodes D1, D2.

The coupler 110 can be a 90-degree coupler for example, then the phasedifference of the radio signals corresponding to the conducting statesand non-conducting states of the diodes D1, D2 is ideally 180 degrees.For example, the phase of the output signal RF ideally can be zerodegrees when the diodes D1, D2 turn off, and the phase of the outputsignal RF ideally can be 180 degrees when the diodes D1, D2 turn on.

The insertion loss can be the minimum if the coupler 110 is a 90-degreecoupler and the phases of the radio signal are 0 and 180 degrees (i.e.the first and second load ends 113, 114 are simultaneously opened orshorted). However, this disclosure does not limit to it. For example,the coupler 110 can be a N-degree coupler, wherein N is not equal to 90.For example, the phases of the radio signal are M1 and M2 degrees,wherein M1 is not equal to 0 and M2 is not equal to 180.

Comparing to replacing the diodes D1, D2 by transistors, which may causehigher insertion loss and lower output power, this embodiment usesdiodes to overcome the aforesaid drawbacks. Further, in this embodiment,the diodes D1, D2 are implemented by PIN diodes, which can use potassiumarsenide as a substrate, can have more advantages than other kinds ofdiodes. Specifically, comparing to the diode, the transistor has greaterparasitic effects between turn-on and turn-off state, such as a largeroff capacitance and conduction inductance, and makes the circuitperformance deterioration. The short-circuit and open-circuit impedancesof a PIN diode can be quite closer among many kinds of diodes so thatthe modulator of this embodiment has better linearity and modulationquality than other kinds of diodes and the transistor for the digitalmodulation system. In addition, the modulator of this embodiment alsohas lower insertion loss, that is, the required local oscillator drivepower of the modulator of this embodiment is smaller and the outputpower of the modulator of this embodiment is larger by the accompaniedeffect of amplitude modulation. Therefore, the modulator of thisembodiment has no additional need of voltage and current conversioncircuit and is ideal for millimeter-wave band applications.

Referring to FIG. 3, FIG. 3 is a detailed circuit diagram of areflective modulator according to an embodiment of the presentdisclosure. In FIG. 3, the DC block unit 120 of the reflective modulator100′ includes a capacitor C1 and a resistor R1, and the DC block unit130 of the reflective modulator 100′ includes a capacitor C2 and aresistor R2. The capacitor C1 is connected between the diode D1 and thefirst load end 113 of the coupler 110. The resistor R1 is connected withthe capacitor C1 and the diode D1. The capacitor C2 is connected betweenthe diode D2 and the second load end 114 of the coupler 110. Theresistor R2 is connected with the capacitor C2 and the diode D2.

The capacitors C1, C2 are used to prevent the DC bias of the diodes D1,D2 from interfering with other circuits, such as the coupler 110. Thecapacitor C1 and the capacitor C2 can have capacitances of 680 uF. Theresistors R1, R2 are used to provide the DC bias path and isolate theoutput signal from the DC path. The larger the resistance of theresistors R1, R2, the better the signal isolation effect of the outputsignal but the worse the bandwidth of the modulator is. To maketradeoff, the resistance of the resistors R1, R2 can be 500 ohms.

In this embodiment, a threshold value T1 for turning on the diode D1equals to V_(d1) I_(d1)*R1, wherein V_(d1) is a diode threshold voltageof the diode D1 and I_(d1) is current flowed through the resistor R1. Athreshold value T2 for turning on the diodes D2 equals to V_(d2)I_(d2)*R2, wherein V_(d2) is a diode threshold voltage of the diode D2and I_(d2) is current flowed through the resistor R2. The thresholdvalue T1 equals to the threshold value T2 when the resistance of theresistor R1 equals to the resistance of the resistor R2 and the diodethreshold voltage of the diode D1 equals to the diode threshold voltageof the diode D2. Therefore, both of the diodes D1, D2 turn on when themessage signal BB is larger than or equal to the threshold values T1,T2, while both of the diodes D1, D2 turn off when the message signal BBis smaller than the threshold values T1, T2.

Referring to FIG. 4, FIG. 4 is a circuit diagram of a BPSK modulatoraccording to an embodiment of the present disclosure. The BPSK modulator200 comprises a balun 210, two identical reflective modulators 100 and apower combiner 220. The reflective modulators 100 connect to the balun,respectively. The power combiner 220 connects to the reflectivemodulators 100, respectively. One message signal BB+ is inputted to oneof the reflective modulators 100 and another one message signal BB− isinputted to another one of the reflective modulators 100. The messagesignal BB+, BB− is a pair of differential signals, that is, the messagesignal BB+, BB− is not all set to low nor all set to high. The balun 210is used to receive an input signal generated from a local oscillator.The power combiner 220 is used to output an output signal RF used forradio frequency.

Referring to FIG. 5, FIG. 5 is a circuit diagram of a BPSK modulatoraccording to an embodiment of the present disclosure. The balun 210 ofthe BPSK modulator 200′ can be a 180 degree balun and has coilconductors 211-214. The coil conductors 211 212 are connected and usedto have equal currents in opposite directions. One end of the coilconductor 213 magnetically couples to the coil conductor 211. Anotherend of the coil conductor 213 connects to ground. One end of the coilconductor 214 magnetically couples to the coil conductor 212. Anotherend of the coil conductor 214 connects to ground.

In FIG. 4 and FIG. 5, an input end of one of the reflective modulators100 connects to the coil conductor 213 and an input end of another oneof the reflective modulators 100 connects to the coil conductor 214. Thepower combiner 220 connects to output ends of the reflective modulators100.

The reflective modulators 100 is used as two-way reflective modulators.For example, when the message signal BB+ is set to high and the messagesignal BB− is set to low, the phase of the output signal RF is ideally 0degrees, which is in a state (−1); and when the message signal BB+ isset to low and the message signal BB− is set to high, the phase of theoutput signal RF is ideally 180 degrees. which is in another state (−2),wherein the two states have the same insertion loss. The message signalsBB+, BB− can be baseband signals. The output signal should be at aminimum value when message signals BB+, BB− have the same bias voltageat half of the high potential. In this case, the circuit is turned off.

The reflective modulators 100 of FIG. 4 and FIG. 5 can be identical tothe reflective modulators 100, 100′ of FIG. 2 and FIG. 3. Therefore, theBPSK modulator of FIG. 4 or FIG. 5 has two couplers, four diodes, fourDC block units and four bias paths in two reflective modulators, whereineach of the four DC block units has a capacitor and a resistor which areconfigured as FIG. 2. However, FIG. 4 and FIG. 5 do not show thedetailed circuit diagrams with above elements for the object ofconvenience. The four diodes can be implemented by PIN diodes which canuse potassium arsenide as a substrate. The BPSK modulator 200, 200′ canbe integrated in a monolithic microwave integrated circuit.

Referring to FIG. 6, FIG. 6 is a circuit diagram of a quadraturemodulator according to an embodiment of the present disclosure. Thequadrature modulator 300 comprises a Wilkinson power divider 310, twoBPSK modulators 200 and a Lange coupler 320. The BPSK modulators 200connect to power output ends of the Wilkinson power divider 310,respectively, for receiving inputs from the Wilkinson power divider 310.The Lange coupler 320 connects to the BPSK modulators 200, respectively,for receiving inputs from the BPSK modulators 200.

Two message signals Q+, Q− are inputted to one of the BPSK modulatorsand another two message signals I+, I− are inputted to another one ofthe BPSK modulators. One of the BPSK modulators generates an outputsignal according to the message signal Q+, Q−. Another one of the BPSKmodulators generates another one output signal according to messagesignal I+, I−. The message signals Q+, Q− can be a pair of differentialsignals, that is, the message signal Q+, Q− is not all set to low norall set to high. The message signal I+, I− can be another one pair ofdifferential signals, that is, the message signal I+, I− is not all setto low nor all set to high.

The Wilkinson Power divider 310 can utilize a Grounded CoplanarWaveguide (GCPW) design to reduce the amplitude and phase error of themodulator while inputting powers to the baluns of the BPSK modulators200 via coplanar waveguide transmission lines.

Two divided power signals from the Wilkinson Power divider 310 can passthrough the BPSK modulators 200, respectively, with the phasecombination of (0°,0°), (0°,180°), (180°, 0°) or (180°,180°). The fourphase combinations of signals outputted from BPSK modulators 200 inputto the Lance coupler 320 and thus the quadrature modulator 300 formsfour different phases of the output signal.

For example, when I+ and Q+ are set to high and I− and Q− are set tolow, the phase of the output signal is ideally 0 degrees, which is in afirst state (−1); when I− and Q+ are set to high and I+ and Q− are setto low, the phase of the output signal is ideally 270 degrees, which isin a second state (−2); when I+ and Q− is set to high and I− and Q+ setto low, the phase of the output signal is ideally 90 degrees, which isin a third state (−3); and when I− and Q− are set high and I+ and Q+ areset low, the phase of the output signal is 180 degrees, which is in afourth state (−4). When all the bias voltages are the same at half ofthe high level, output signal is at a minimum value. In this case, thecircuit is turned off.

The BPSK modulators 200 of FIG. 6 can be identical to the BPSKmodulators 200, 200′ of FIG. 4 and FIG. 5. Therefore, the quadraturemodulator 300 of FIG. 6 has four couplers, eight diodes, eight DC blockunits and eight bias paths in the two BPSK modulators 200, wherein eachof the eight DC block units has a capacitor and a resistor which areconfigured as FIG. 2. However, FIG. 6 does not show the detailed circuitdiagrams with above elements for the object of convenience. The eightdiodes can be implemented by PIN diodes which can use Potassium arsenideas a substrate. The quadrature modulator 300 can be integrated in amonolithic microwave integrated circuit.

In a higher-level digital modulation system, the quadrature modulator ofthe present disclosure can achieve any amplitude and phase control.Specifically, the design method can adopt two sets of reflectivetwo-phase modulators, 90-degree couplers and power combiners. The90-degree couplers mainly provide orthogonal carrier signals andgenerate individual orthogonal carrier signals for further input to twosets of reflective two-phase modulation. The modulating signals of therespective modulations are then combined by the power combiner. If thetwo-phase modulator only 0 and 180 degrees phase modulation function,the quadrature modulator can only produce 0, 90, 180 and 270 degreesphase modulation. To increase the amplitude and phase modulation, suchas n-QAM higher-level digital modulation, two-phase reflective modulatormust also have a linear amplitude modulation capability, by the linearmodulation of the orthogonal carrier signal, arbitrary amplitude andphase modulation signal can be generated.

In conclusion, the aforesaid signal modulators feature broadband, lowinsertion loss, low required local oscillation drive power, low phaseand amplitude imbalance, excellent modulation quality and small requireddie area.

The present disclosure is disclosed above by preferred embodiments.However, persons skilled in the art should understand that the preferredembodiments are illustrative of the present disclosure only, but shouldnot be interpreted as restrictive of the scope of the presentdisclosure. Hence, all equivalent modifications and replacements made tothe aforesaid embodiments should fall within the scope of the presentdisclosure. Accordingly, the legal protection for the present disclosureshould be defined by the appended claims.

What is claimed is:
 1. A reflective modulator comprises: a couplerhaving an input end, an output end, a first load end and a second loadend, the input end being used to receive an input signal, the output endbeing used to output an output signal; a first diode; a second diode; afirst DC (Direct Current) block unit connected between the first diodeand the first load end of the coupler for DC blocking; and a second DCblock unit connected between the second diode and the second load end ofthe coupler for DC blocking; wherein a message signal is inputted toboth of the first and second DC block units for operating the states ofthe first and second diodes.
 2. The reflective modulator of claim 1,wherein the first and second diodes turn on when the message signal islarge enough, and the first and second diodes turn off when the messagesignal is not large enough.
 3. The reflective modulator of claim 1,wherein the first DC block unit includes a first capacitor and a firstresistor, the second DC block unit includes a second capacitor and asecond resistor, the first capacitor is connected between the firstdiode and the first load end of the coupler for DC blocking, the firstresistor is connected with the first capacitor and the first diode, thesecond capacitor is connected between the second diode and the secondload end of the coupler for DC blocking, and the second resistor isconnected with the second capacitor and the second diode.
 4. Thereflective modulator of claim 1, wherein the first and second diodes areimplemented by PIN diodes.
 5. The reflective modulator of claim 1,wherein the input signal is generated from a local oscillator and theoutput signal is used for radio frequency.
 6. A BPSK (Binary Phase ShiftKeying) modulator comprises: a balun having a first conductor, a secondconductor, a third conductor and a fourth conductor, the first conductorand the second conductor is connected and used to have equal currents inopposite directions, one end of the third conductor magneticallycoupling to the first conductor and another end of the third conductorconnecting to ground, one end of the fourth conductor magneticallycoupling to the second conductor and another end of the fourth conductorconnecting to ground; a first reflective modulator, wherein a firstinput end of the first reflective modulator is connected to the thirdconductor; a second reflective modulator, wherein a second input end ofthe second reflective modulator is connected to the fourth conductor;and a power combiner connected to a first output end of the firstreflective modulator and a second output end of the first reflectivemodulator, wherein a first message signal is inputted to the firstreflective modulator and a second message signal is inputted to thesecond reflective modulator, and the first message signal and the secondmessage signal are a pair of differential signals; wherein the firstreflective modulator comprises a first coupler, a first diode, a seconddiode, a first DC (Direct-Current) block unit and a second DC blockunit, the first coupler having the first input end, the first outputend, a first load end and a second load end, the first DC block unitconnecting between the first diode and the first load end of the firstcoupler for DC blocking, the second DC block unit connected between thesecond diode and the second load end of the first coupler for DCblocking, the first message signal inputting to both of the first andsecond DC block units for operating the state of the first and seconddiodes; wherein the second reflective modulator comprises a secondcoupler, a third diode, a fourth diode, a third DC block unit and afourth DC block unit, the second coupler having the second input end,the second output end, a third load end and a fourth load end, the thirdDC block unit connecting between the third diode and the third load endof the second coupler for DC blocking, the fourth DC block unitconnecting between the fourth diode and the fourth load end of thesecond coupler for DC blocking, the second message signal inputting toboth of the third and fourth DC block units for operating the state ofthe third and fourth diodes.
 7. The BPSK modulator of claim 6, whereinthe first and second diodes turn on when the first message signal islarge enough, and the first and second diodes turn off when the firstmessage signal is not large enough; and wherein the third and fourthdiodes turn on when the second message signal is large enough, and thethird and fourth diodes turn off when the second message signal is notlarge enough.
 8. The BPSK modulator of claim 6, wherein the first DCblock unit includes a first capacitor and a first resistor, the secondDC block unit includes a second capacitor and a second resistor, thefirst capacitor is connected between the first diode and the first loadend of the first coupler for DC blocking, the first resistor isconnected with the first capacitor and the first diode, the secondcapacitor is connected between the second diode and the second load endof the first coupler for DC blocking, and the second resistor isconnected with the second capacitor and the second diode.
 9. The BPSKmodulator of claim 8, wherein the third DC block unit includes a thirdcapacitor and a third resistor, the fourth DC block unit includes afourth capacitor and a fourth resistor, the third capacitor is connectedbetween the third diode and the third load end of the second coupler forDC blocking, the third resistor is connected with the third capacitorand the third diode, the fourth capacitor is connected between thefourth diode and the fourth load end of the second coupler for DCblocking, and the fourth resistor is connected with the fourth capacitorand the fourth diode.
 10. The BPSK modulator of claim 6, wherein thefirst, second, third and fourth diodes are implemented by PIN diodes.11. The BPSK modulator of claim 6, wherein an input signal is generatedfrom a local oscillator and inputted to the balun, and an output signalis outputted from the power combiner and used for radio frequency. 12.The BPSK modulator of claim 6, wherein the BPSK modulator is integratedin a monolithic microwave integrated circuit.
 13. A quadrature modulatorcomprises: a Wilkinson power divider having a power input end, a firstpower output end and a second power output end; a first BPSK (BinaryPhase Shift Keying) modulator connected to the first power output end ofthe Wilkinson power divider; a second BPSK modulator connected to thesecond power output end of the Wilkinson power divider, the second BPSKmodulator generating a second output signal; and a Lange couplerconnected to the first BPSK modulator and the second BPSK modulator forreceiving a first output signal and a second output signal, wherein afirst message signal and a second message signal are inputted to thefirst BPSK modulator, a third message signal and a fourth message signalare inputted to the second BPSK modulator, the first BPSK modulatorgenerates the first output signal according to the first message signal,the second message signal, and an input from the Wilkinson powerdivider, and the second BPSK modulator generates the second outputsignal according to the third message signal, the fourth message signal,and an input from the Wilkinson power divider, wherein the first BPSKmodulator comprises a first balun, a first reflective modulator, asecond reflective modulator and a first power combiner, the first balunhaving a first conductor, a second conductor, a third conductor and afourth conductor, the first conductor and the second conductor beingconnected and used to have equal currents in opposite directions, oneend of the third conductor magnetically coupling to the first conductorand another end of the third conductor connecting to ground, one end ofthe fourth conductor magnetically coupling to the second conductor andanother end of the fourth conductor connecting to ground, a first inputend of the first reflective modulator connecting to the third conductor,a second input end of the second reflective modulator connecting to thefourth conductor, the first power combiner connecting to a first outputend of the first reflective modulator and a second output end of thesecond reflective modulator, the first message signal inputting to thefirst reflective modulator, the second message signal inputting to thesecond reflective modulator, the first message signal and the secondmessage signal being a pair of differential signals; wherein the secondBPSK modulator comprises a second balun, a third reflective modulator, afourth reflective modulator and a second power combiner, the secondbalun having a fifth conductor, a sixth conductor, a seventh conductorand an eighth conductor, the fifth conductor and the sixth conductorbeing connected and used to have equal currents in opposite directions,one end of the seventh conductor connecting to the fifth conductor andanother end of the seventh conductor connecting to ground, one end ofthe eighth conductor connecting to the sixth conductor and another endof the eighth conductor connecting to ground, a third input end of thethird reflective modulator connecting to the seventh conductor, a fourthinput end of the fourth reflective modulator connecting to the eighthconductor, the second power combiner connecting to a third output end ofthe third reflective modulator and a fourth output end of the fourthreflective modulator, the third message signal inputting to the thirdreflective modulator, the fourth message signal inputting to the fourthreflective modulator, the third message signal and the fourth messagesignal being a pair of differential signals; wherein the firstreflective modulator comprises a first coupler, a first diode, a seconddiode, a first DC (Direct-Current) block unit and a second DC blockunit, the first coupler having the first input end, the first outputend, a first load end and a second load end, the first diode connectingto the first load end of the first coupler, the second diode connectingto the second load end of the first coupler, the first DC block unitconnecting between the first diode and the first load end of the firstcoupler for DC blocking, the second DC block unit connected between thesecond diode and the second load end of the first coupler for DCblocking, the first message signal inputting to both of the first andsecond DC block units for operating the state of the first and seconddiodes; wherein the second reflective modulator comprises a secondcoupler, a third diode, a fourth diode, a third DC block unit and afourth DC block unit, the second coupler having the second input end,the second output end, a third load end and a fourth load end, the thirddiode connecting to the third load end of the second coupler, the fourthdiode connecting to the fourth load end of the second coupler, the thirdDC block unit connecting between the third diode and the third load endof the second coupler for DC blocking, the fourth DC block unitconnecting between the fourth diode and the fourth load end of thesecond coupler for DC blocking, the second message signal inputting toboth of the third and fourth DC block units for operating the state ofthe third and fourth diodes; wherein the third reflective modulatorcomprises a third coupler, a fifth diode, a sixth diode, a fifth DCblock unit and a sixth DC block unit, the third coupler having the thirdinput end, the third output end, a fifth load end and a sixth load end,the fifth diode connecting to the fifth load end of the third coupler,the sixth diode connecting to the sixth load end of the third coupler,the fifth DC block unit connecting between the fifth diode and the fifthload end of the third coupler for DC blocking, the sixth DC block unitconnecting between the sixth diode and the sixth load end of the thirdcoupler for DC blocking, the third message signal inputting to both ofthe fifth and sixth DC block units for operating the state of the fifthand sixth diodes; and wherein the fourth reflective modulator comprisesa fourth coupler, a seventh diode, an eighth diode, a seventh DC blockunit and an eighth DC block unit, the fourth coupler having the fourthinput end, the fourth output end, a seventh load end and a eighth loadend, the seventh diode connecting to the seventh load end of the fourthcoupler, the eighth diode connecting to the eighth load end of thefourth coupler, the seventh DC block unit connecting between the seventhdiode and the seventh load end of the fourth coupler for DC blocking,the eighth DC block unit connecting between the eighth diode and theeighth load end of the fourth coupler for DC blocking, the fourthmessage signal inputting to both of the seventh and eighth DC blockunits for operating the state of the seventh and eighth diodes.
 14. Thequadrature modulator of claim 13, wherein the first and second diodesturn on when the first message signal is large enough, and the first andsecond diodes turn off when the first message signal is not largeenough; wherein the third and fourth diodes turn on when the secondmessage signal is large enough, and the third and fourth diodes turn offwhen the second message signal is not large enough; wherein the fifthand sixth diodes turn on when the third message signal is large enough,and the fifth and sixth diodes turn off when the third message signal isnot large enough; and wherein the seventh and eighth diodes turn on whenthe fourth message signal is large enough, and the seventh and eighthdiodes turn off when the fourth message signal is not large enough. 15.The quadrature modulator of claim 13, wherein the first DC block unitincludes a first capacitor and a first resistor, the second DC blockunit includes a second capacitor and a second resistor, the firstcapacitor is connected between the first diode and the first load end ofthe first coupler for DC blocking, the first resistor is connected withthe first capacitor and the first diode, the second capacitor isconnected between the second diode and the second load end of the firstcoupler for DC blocking, and the second resistor is connected with thesecond capacitor and the second diode; wherein the third DC block unitincludes a third capacitor and a third resistor, the fourth DC blockunit includes a fourth capacitor and a fourth resistor, the thirdcapacitor is connected between the third diode and the third load end ofthe second coupler for DC blocking, the third resistor is connected withthe third capacitor and the third diode, the fourth capacitor isconnected between the fourth diode and the fourth load end of the secondcoupler for DC blocking, and the fourth resistor is connected with thefourth capacitor and the fourth diode; wherein the fifth DC block unitincludes a fifth capacitor and a fifth resistor, the sixth DC block unitincludes a sixth capacitor and a sixth resistor, the fifth capacitor isconnected between the fifth diode and the fifth load end of the thirdcoupler for DC blocking, the fifth resistor is connected with the fifthcapacitor and the fifth diode, the sixth capacitor is connected betweenthe sixth diode and the sixth load end of the third coupler for DCblocking, and the sixth resistor is connected with the sixth capacitorand the sixth diode; and wherein the seventh DC block unit includes aseventh capacitor and a seventh resistor, the eighth DC block unitincludes a eighth capacitor and a eighth resistor, the seventh capacitoris connected between the seventh diode and the seventh load end of thefourth coupler for DC blocking, the seventh resistor is connected withthe seventh capacitor and the seventh diode, the eighth capacitor isconnected between the eighth diode and the eighth load end of the fourthcoupler for DC blocking, and the eighth resistor is connected with theeighth capacitor and the eighth diode.
 16. The quadrature modulator ofclaim 13, wherein the first, second, third, fourth, fifth, sixth,seventh and eighth diodes are implemented by PIN diodes.
 17. Thequadrature modulator of claim 13, wherein an input signal inputted tothe power input end of Wilkinson power divider is generated from a localoscillator, and an output signal is outputted from the Lange coupler andused for radio frequency.
 18. The quadrature modulator of claim 13,wherein the quadrature modulator is integrated in a monolithic microwaveintegrated circuit.